1. Field of the Invention
The present invention is related to sensing devices which are responsive to temperature, and which can be heated by the application of an electrical current. In particular, the present invention relates to an integrated semiconductor resistance temperature sensor and thin film resistance heater.
2. Description of the Prior Art
There are a number of sensing applications in which a resistance temperature sensor can be used to sense, in an indirect manner, some other parameter. One example is the sensing of mass flow of a fluid in which two resistance temperature sensors are positioned along the flow path. One of the resistance temperature sensors is heated by a flow of electrical current through that temperature sensor or by heat from an adjacent heating element. The rate of heat loss of the heated temperature sensor is dependent upon the mass flow rate past the sensor. The energy required to maintain the resistance of the heated temperature sensor at a constant value (and therefore constant temperature) is a measure of the mass flow.
In the past, hot wire anemometers have been used for this mass flow measurement. There have been, however, various attempts to develop smaller and lower cost temperature sensors for use in mass flow measurement. There remains a need for improved sensors which are low cost, are easily fabricated on a large volume reproducible basis, are very small size, and are compatable with simple and low cost drive and sensing circuitry.